Trans-catheter aortic valve replacement (“TAVR”) has been shown to improve the survival rate in high risk patients for whom surgical heart valve replacement is not an option. However, the long-term clinical success of a TAVR or any trans-catheter aortic valve implantation (“TAVI”) procedure is dependent on accurate deployment, anchoring and acceptable valve performance, both acutely and chronically. This requires maximum reduction or potential elimination of the risks associated with paravalvular (PV) aortic regurgitation (AR). An additional factor that contributes to the problem of selecting a proper valve size is the eccentricity/elliptical nature of the cross-section of the native valve annulus.
There are a number of ways in which the valve annulus may be sized. Current techniques include imaging techniques such as trans-thoracic echocardiogram (TTE), trans-esophageal echocardiogram (TEE), and angiography. However, these imaging methods are not standardized and may yield different results depending on the view obtained of the annulus with the annulus' elliptic shape contributing to the uncertainty. Although valve-sizing using 3D computed tomographic (CT) imaging has been observed to result in less PV AR, this technique is expensive and requires independent patient preparation/assessment prior to the implantation or valvuloplasty procedure and also poses the risk of exposure to harmful radiation. Thus, there is a clinical need for an alternative option for TAVI sizing that is cost effective.
In addition, alterations to the valve annulus following a balloon valvuloplasty procedure can make it difficult to correctly size the annulus, even with current imaging techniques. For example, it is expected that a valve's annulus dimensions are altered after a balloon valvuloplasty procedure, intended to open up the diseased native valve. However, some imaging techniques, like CT, are performed pre-procedurally and do not provide the altered dimensions of the annulus after this procedure has been performed.